Exposure apparatuses such as a reduction projection exposure apparatus using a step-and-repeat system (i.e., a stepper) and a scanning projection exposure apparatus using a step-and-scan system (i.e., a scanning stepper) are used during a lithography process in manufacturing semiconductor elements, liquid crystal display elements, etc. As semiconductor elements become more highly integrated, there is a demand that these exposure apparatuses fabricate finer circuit patterns on a photosensitive substrate.
To make the circuit pattern finer, imaging characteristics of a projection optical system that projects a pattern image of a mask onto a photosensitive substrate must be adjusted to a best possible level. To adjust the imaging characteristics, there are methods of determining an amount of distortion of the projection optical system.
For example, in a method disclosed in Patent Literature 1, a reticle blind and the like is used in limiting an exposure region such that, after the projection optical system exposes a plurality of first patterns on a photosensitive substrate, only a second pattern can be exposed; the second pattern is exposed over a latent image of the first patterns by moving the photosensitive substrate by fixed amounts based on the design-dependent arrangement of the first patterns, and the distortion amount of the projection optical system is determined by measuring the latent images of the first and second patterns. Developed patterns can be used instead of latent images of the patterns.
Patent Literature 1: Japanese Unexamined Patent Publication No. S64-068926